In a communication system, such as a wireless communication system, devices may communicate with one another via an intermediary device. For example, a wireless station and user equipment (UE) may communicate via a repeater. In some instances, the wireless station, UE and/or the repeater may include multiple antennas (e.g., a multiple-input multiple-out (MIMO) device).
In the case of intermediate devices, such as a repeater, the intermediate device may perform various operations with respect to received and/or forwarded transmissions. For example, the repeater may amplify a received transmission and forward the transmission to another device. Depending on the repeater, the repeater sometimes may not adapt its filtering or amplification for transmissions received and forwarded based on a channel state that exists between the repeater and another device (e.g., the wireless station or the UE). In other instances, however, the repeater may adapt its filtering or amplification for transmissions received and forwarded. For example, the repeater may utilize first hop channel state information (CSI) to perform various operations (e.g., singular value decomposition (SVD) beamforming or spatial filtering (e.g., linear minimum mean-squared error (LMMSE) or least square). While both of these types of repeaters may provide a significant degree of transparency, these repeaters may be limited in enhancing the rate-coverage performance of the communication system.
In more sophisticated repeaters, the repeater may utilize first hop CSI and second hop CSI. For example, the repeater may obtain SVD of the channels of the first and second hops. However, it is difficult to obtain the second hop CSI before forwarding a received transmission while simultaneously maintaining transparency in the communication system. For example, the repeater may create additional overhead (e.g., signaling) to the second hop device to obtain the second CSI.